The characteristic morphology of cells is controlled in information in the genome, and expressed through the organization of cytoplasmic structures and the cell surface. The underlying molecular mechanisms of that expression are not understood. Some transformed cells which do not display differentiated shape can be induced to spread and take their typical morphology. Several results strongly suggest that the components and information necessary for assumption of differentiated morphology can reside in the cytoplasm. We have recently used such a cell system to study specification of morphology at the cytoplasmic level. Mouse neuroblastoma, and established line of transformed cells, grow round in culture, but they can be induced to extend axon-like neurites and so resemble their normal counterparts. The patterns of neurites form an extremely wide repertoire of morphologies. However, the majority of mitotic sister cells are uniquely related to one another in considerable detail. The results suggest that sister cells share determinants of specific cell shape. This system presents a striking and easily visualized example of morphological control at the cytoplasmic level. We will use it as a tool to study the structural and molecular basis for the storage, expression and mitotic transmission of the morphological determinants. In particular, we will determine the persistence of the determinants through subsequent rounds of cell division. We will address the role of the cytoskeleton -- microtubles and using specific drugs and microscopic techniques. We will examine the influence substrate -- in guiding neurite outgrowth. These experiments will address a fundamental question in cell and developmental biology, with relevance to the transformed phenotype: how are cellular components organized to produce a particular morphology?